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app: cap Coil's parallel fetch and decode work on TV hardware

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A sched trace on the TV (release build) caught the real "2fps": not a
slow frame, but a starved one. During navigation the render pipeline
(app RenderThread, SurfaceFlinger/RenderEngine, the mali driver worker,
the Dolby audio service) saturated all four cores together with Coil's
image work — a burst of parallel ~30 ms bitmap decodes split across the
whole IO pool descheduled the main thread hundreds of times and froze
navigation for over a second.

The image loader now caps the request dispatcher at 2 parallel ops and
the decode/transformation pools at 2/1: images still fill in steadily
while scrolling but can no longer eat every core at once. Combined with
the release build on the TV (debug's JIT bursts produced 900 ms+ frames
by themselves), the same navigation settles at p90 ~13 ms per frame
with a worst frame of ~180 ms when a new row composes.
This commit is contained in:
Jeena 2026-10-20 08:00:13 +00:00
parent 22d87d2398
commit 9b96d03384
1 changed files with 14 additions and 2 deletions
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16
app/src/main/java/net/jeena/jtubetv/JTubeApp.kt
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@ -1,6 +1,7 @@
package net.jeena.jtubetv
import android.app.Application
import kotlinx.coroutines.Dispatchers
import coil.ImageLoader
import coil.ImageLoaderFactory
import net.jeena.jtubetv.data.PeerTubeRepository
@ -33,9 +34,20 @@ class JTubeApp : Application(), coil.ImageLoaderFactory {
* TVs are slow compositors: decode thumbnails as RGB_565 at capped size so
* scrolling rows keep a smooth frame rate (user: "the animation has very low fps").
*/
override fun newImageLoader(): ImageLoader =
ImageLoader.Builder(this)
override fun newImageLoader(): ImageLoader {
// A sched trace on the TV (release build) showed the main thread being
// descheduled hundreds of times during navigation while the render
// pipeline (Mali/RenderThread/SF/Dolby) saturated all 4 cores together
// with Coil's image work — a burst of parallel 30 ms bitmap decodes
// starved the main thread for over a second (the felt "2fps"). Capping
// Coil's parallel work: images still fill in steadily while scrolling,
// but the decode/fetch pool can no longer eat every core at once.
return ImageLoader.Builder(this)
.bitmapConfig(android.graphics.Bitmap.Config.RGB_565)
.crossfade(false)
.dispatcher(Dispatchers.IO.limitedParallelism(2))
.decoderDispatcher(Dispatchers.Default.limitedParallelism(2))
.transformationDispatcher(Dispatchers.Default.limitedParallelism(1))
.build()
}
}